1. Field
The disclosed aspects relate generally to enabling communications using a power amplifier (PA) and specifically to methods and systems for predicting a control signal for a PA switcher and/or a predicted supply voltage for a digital pre-distortion module associated with the PA.
2. Background
Current PA control apparatuses and methods are generally configured to use one or more combination of four PA control schemes. First, a battery direct scheme directly connects the battery to the PA. This may be efficient at times when max power is needed, but at lower powers efficiency drops rapidly because it's not necessary to use full battery voltage. Second, an average power tracking (APT) scheme uses a third party switcher between the batter and PA and uses an algorithm to change voltage between power control groups. Compared to the battery direct scheme, at lower powers efficiency falls off more gradually since PA voltage is correspondingly decreased. Third, a super APT (SAPT) scheme uses an algorithm to change voltage per various power control groups and also uses predistortion and adaptiveness to squeeze voltage to limits. Fourth, envelope tracking (ET) uses a separate chipset to track the signal envelope at high speed and high precision. This scheme may require PAs optimized for ET usage and may require an ET digital to analog converter (DAC) on the mobile station modem (MSM).
Further, Power amplifiers typically do not behave in a linear manner. More particularly, power amplifier distortion may compress or may expand the output signal swing of the amplifier. Signal detectors receiving and decoding the amplified signals typically do not operate in such a non-linear fashion. Therefore, it is typically necessary to linearize the output of the amplifier. One approach to such linearization is digital predistortion. Digital predistorters may be used with power amplifiers to invert the power amplifier distortion characteristics by expanding the compression regions and compressing the expansion regions in the power amplifier characteristics curve.
Both PA control schemes and digital predistortion schemes would benefit from knowledge of future signal characteristics. As such, a system and apparatus that predicting a control signal for a PA switcher and/or a predicted supply voltage for a digital pre-distortion module associated with a PA may be desired.